1. Field of the Invention
Apparatus and method are provided for locating and performing an operation in a wellbore with respect to a reference perforation. More specifically, forming perforations in the casing of wells at a selected location with respect to a reference perforation, cleaning perforations at a selected location and jet drilling through perforations at a selected location into an underground formation surrounding the casing are disclosed.
2. Description of Related Art
Perforations are formed in the casing of wells to allow fluid to pass to or from the wellbore. Perforations are usually formed by shaped charges, using well known technology. It is also well known to form perforations by abrasive jets. Often, the perforations in wells become plugged or partially plugged or “damaged,” which decreases the ability to produce or inject fluids through the wells. A large variety of chemical, mechanical and hydraulic methods have been proposed for decreasing or removing damage to flow in perforations. An example of a hydraulic method is that disclosed in U.S. Pat. No. 5,060,725, where the use of multiple jets created by pumping fluid downhole and through a tool containing multiple nozzles is disclosed. The tool is rotated and reciprocated inside a casing while pumping high-pressure fluid through the nozzles to wash perforations. Jet drilling of drainholes from wells is also well known. For example, U.S. Pat. No. 6,668,948 discloses a nozzle suitable for drilling through the casing of a well to form a perforation and then continued drilling into the surrounding formation before the nozzle is withdrawn into the well.
What is needed is apparatus and method for forming a perforation in casing in a selected location with respect to a reference perforation, jet cleaning a perforation that is located at a selected location with respect to a reference perforation by a stationary fluid jet that is concentrated on that perforation and drilling a drain hole through a perforation that is at a selected location with respect to a reference perforation.